[c-nsp] Layer Two tunneling question (advice needed)

[John Neiberger]

I've never had to configure any sort of layer two tunneling, so I'm
not really familiar with my options. I'm pretty sure there are many
here who have done this, so I thought I'd ask. What we need to do is
fairly simple. Here's a basic map:


DeviceA ------ [6500] -------(fiber run to different site)--------
[6500] ------- DeviceB

At the moment, the devices on each end are connected to layer three
interfaces, not switchports, and the link between the 6500s is routed.
We've run into a legacy issue and the solution is to put DeviceA and
DeviceB on the same vlan. However, we do not want to change the
routing between the 6500s. We really, *really* want to leave the
routing in place. Switching to an all layer-two design causes some
other headaches for us that you don't see because of my simplified
diagram.

So, I think some sort of layer two tunneling is in order. What are our
options if we want to make DeviceA and DeviceB think they're local to
each other and in the same LAN? I've heard of L2TP and of various MPLS
techniques that might solve this, but I've just never needed to use
them and really know nothing about how they're configured or if
they're even legitimate options.

Any thoughts?

Many thanks!
John